Plastic hardness qualifies the resistance to penetration of a plastic by a harder body. The harder material wears or scratches the softer material.
It’s a key engineering parameter for constructing devices, consumer products or industrial parts. This can become evident when considering cosmetic effects such as scratching or loss of surface gloss from the rubbing of two materials. Alternatively, one can consider wear from moving parts.
How Is it Measured?
There are a number of empirical hardness scales that have been constructed over time to try to replicate conditions of scratching, rubbing, wear between two materials. These methods aim to give a relative ranking of the hardness of two materials. There is no underlying theory for how they work.
Two scales are frequently used:
Which Hardness Scale Should You Use?
The different hardness scales seem to have more popularity in different parts of the world, in different industries and in different disciplines. For someone just beginning to become interested in “HARDNESS” as a key indicator of performance, it is suggested to examine data sheets and literature references for the relevant industry, disciple or geographical region.
When making comparisons for purposes of promoting a product or material: one has to speak the language of one’s peers. There are a multitude of possibilities each having a different rationale which go beyond this comparative treatise.
Here is a correspondence table between the most common methods. It gives an idea of the order of magnitude, but we do not recommend conversion between the scales.
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